<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 1200px;
            height: 400px;
            background-color: #ffffff;
            margin: auto;
        }
        .box>div{
            height: 400px;
            background-color: #88ff84;

            /* 块级--->行内块 */
            /* display: inline-block; */

            /* 浮动 */
            float: left;
            margin-right: 12.5px;
        }
        .d1{
            width: 280px; 
        }
        .d2{
            width: 700px;
        }
        .d3{
            width: 180px;
        }

    </style>
</head>
<body>
    <div class="box">
        <div class="d1"></div>
        <div class="d2"></div>
        <div class="d3"></div>
    </div>
</body>
</html>